The present invention relates to gear shifting control of a vehicle gearbox having at least one power source, such as an internal combustion traction engine and/or an electrical traction machine.
More specifically, it relates to a method for controlling the synchronization of a pinion rotating on a primary shaft driven by a traction machine of the vehicle, and rotatably connected to a secondary shaft of a parallel shaft gearbox, without synchronization mechanisms. This method is based on sending to the traction machine, before coupling of the pinion on the primary shaft, a torque command to minimize the difference between the primary speed and the secondary speed multiplied by the reduction ratio between these two shafts.
This invention is applicable to all parallel shaft transmissions, wherein gear changes are made by moving a coupling means without synchronizing rings, particularly in electric and hybrid drive trains.
When a system of coupling by engagement of a sliding gear on the pinions has no mechanical synchronization means, the rotating elements can be synchronized by controlling the primary speed of the gearbox. This controlling requires precise control of the speed by the traction machine in order to avoid torque shocks.
Publication FR 2 988 799 discloses a known method for synchronizing a pinion with its shaft, without a mechanical synchronizer. According to this method, the traction machine of the vehicle is controlled to minimize the difference between the primary speed and the secondary speed of the gearbox, multiplied by the gear ratio between the two shafts. The advantage of the process is to maintain the control of the traction machine until the speeds of the electrical machine shaft and the shaft connected to the wheels are completely equalized, to within the gear ratio. However, its accuracy comes up against the inertia of the traction machine and its time of response to the torque control instructions, especially when this traction machine is an internal combustion engine. The main difficulties are encountered during hard braking, on a steep slope.
In order for shifting to take place in satisfactory conditions, the operation must be completely transparent for the driver, while continuing to meet the demand for torque at the wheel. In particular, the speed difference must reach the 30 rpm (rotations per minute) range very rapidly.